In general, when a metal substrate such as aluminum, etc., is coated with fluororesins, a primer is applied on the substrate, and then topped with a fluororesin alone to form a two-layer coating. However, when such fluororesin coatings repeatedly make contact with materials having a higher hardness than the fluororesin, the coating is worn out. To prevent this, in general, filler such as mica is included in the topcoating layer for improved wear resistance.
For improving the wear resistance of fluororesin coating layers, adding an inorganic powder with a new Mohs hardness of 8 to fluororesin was proposed in Japanese Kokoku Patent No. HEI 3[1991]-14194, and a method for imparting sufficient hardness to fluororesin films by dispersing superfine diamond particles in the topcoating layer was proposed in Japanese Kokai Patent No. HEI 7[1995]-67784. However, these applications, fillers are included in the fluororesins, thus heat and moisture infiltration can easily occur, leading to substrate corrosion and problems of layer separation between the substrate and primer layer or primer layer and topcoating layer, or the primer layer interior.
Thus, it is desirable that the present invention provide fluororesin coating films with improved penetration resistance, while maintaining excellent wear resistance. It is further desirable that the present invention provide products having fluororesin coating films with excellent wear resistance and improved penetration resistance.